What is it about?
The two phototropins of Arabidopsis thaliana, phot1 and phot2, are characterized by different light sensitivities, though they share highly redundant functions. They both control phototropism, leaf expansion,stomatal opening, and the chloroplast accumulation response. Only phot1 mediates the inhibition of the hypocotyl growth reaction, and only phot2 mediates chloroplast avoidance and dark positioning.
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Why is it important?
Phototropins elevate cytosolic Ca2+ after activation by blue light. In higher plants, both types of chloroplast responses depend on Ca2+, and internal calcium stores seem to be crucial for these processes. To characterize the localization of calcium in Arabidopsis mesophyll cells, loosely bound (exchangeable) Ca2+ was precipitated with potassium pyroantimonate and analyzed by transmission electron microscopy followed by energy-dispersive X-ray microanalysis.
Perspectives
In the phot2 and phot1phot2 mutants, calcium patterns were different from those of wild-type plants. In both mutants, no elevation of calcium after blue light treatment was observed at the cell periphery (including the cell wall and a fragment of cytoplasm). This result confirms the involvement of phototropin2 in the regulation of Ca2+ homeostasis in mesophyll cells.
Professor Elzbieta Wyroba
Nencki Institute of Experimental Biology
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This page is a summary of: Blue light-dependent changes in loosely bound calcium in Arabidopsis mesophyll cells: an X-ray microanalysis study, Journal of Experimental Botany, March 2016, Oxford University Press (OUP),
DOI: 10.1093/jxb/erw089.
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